Production of paraffins



April 30, 1946.

M. P. MATUSZAK PRODUCTION OF PARAFFIINS Filed Dec. 4, 1942 BY WIM, *W

A TTORNEYS Patented Apr. 30, im

PRODUCTION F PARAFFINS Maryan P. Matuszak, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation o! Delaware Application December 4, 1942, Serial No.487.872

7 Claims.

This invention relates to a process for reacting paraillns and oleilns in the presence of a liquid acid-type catalyst to produce other paralns. More specifically, in one modification, it relates to the production of especially desirable paramns different in molecular structure from the products resulting from simple junctures of the original parafllns and olens. This application is a continuation-in-part of copending application, Serial No. 404,395, iled July 28, 1941.

In present-day acid-catalyzed alkylation processes for reacting paramns with olens to produce heavier parailns, the principal or major constituents of the alkylates produced under ordinary good reaction conditions are those which would be formed if one olefin molecule added to one paran molecule by a reaction generally termed paraln-oleiin juncture. At least in some cases, apparently a methyl group from the original paraffin becomes attached to one of the two double-bond carbon atoms of the original olefin and the rest of the original paraiiin becomes at tached to the other double-bond carbon atom of the original olefin. In any event the number of carbon atoms per molecule of the major chemical components of the product is equal to the sum ofthe numbers of carbon atoms per molecule ci the paramn and olefin reactants. Further,

p only a limited number or the many paraiiln isomers characterized by this number of carbon atoms per molecule are formed as primary products of simple paraffin-alena junctures, although other isomers may be formed in small proportions by so-called secondary and side reactions, such as isomerization of the primary product, dimerization of the original oleln accompanied or followed by hydrogenation of the dlmerfand the like.

Those skilled in the art of alkylation have hitherto directed their efforts mainly towards increasing the extent of the simple parafn-olefin juncture and towards decreasing the extent oi side reactions, especially polymerization of the olen. However, in many instances, specific side reactions other than polymerization produce con-l stituents in the alln'late that are more desirable than those produced by the juncture of the initial paratlin with the initial olefin. Further, these specific desirable side reactions may be greatly kand selectively promoted in accordance with the concept ofthe present invention.

One object of my invention is to react hydro carbons to produce other hydrocarbons.

An object of this invention isto yproduce paraillns vloyal: lalkylation process wherein certain lli desirable side reactions, which ordinarily occur to only a limited extent, are selectively promoted so that they occur to a much larger extent.

Another object of this invention is so to react isobutane and an olen other than isobutylene and having three to ve carbon atoms per molecule as to obtain high yields of 2,2,4-trimethyl pentane (isooctane).

A further object oi my invention is to produce paraiiln hydrocarbons.

Another object of this invention is to produce isooctane, which has eight carbon atoms per molecule, from isobutane and propylene, which have four and three carbon atoms per molecule, respectively.

Another object of this invention is to increase the proportion of 2,2,4-trimethylpentane produced by reacting isobutane and butene-2 in the presence of a liquid acid-type alkylatlon catalyst.

Another object oi this invention is to increase the proportions of 2,2,4-trimethylpentane and 2,3,d-trimethylpentane produced by reacting isobutane and butene-l in the presence of a liquid acid-type allrylation catalyst.

another object of this invention is to increase the total yield oi higher boiling and normally liquid or gasoline-range parafflns produced from a given weight of an olenic reactant in acidcatalyzed conversion of isopentane to heavier paraiiins.

Another object oi this invention is to produce high proportions of isobutane and isohexanes from isopentane and an olefin in the presence of a liquid acid-type alkylation catalyst.

Other objects and advantages of this invention will appear from the accompanying description and discussion.

This invention, in a broad sense, comprises producing from paraillns and oleflns in the presence of a liquid acid-type alkylatlon catalyst desirable saturated hydrocarbons having molecular structures dierent from those of the products of simple primary junctures of the original paraffins and oleflns. In a more limited sense, it comprises selectively producing specific parans which are normally not present or at most present in only relatively small proportions in the products from acid-catalyzed alkylations of the original paramns with the original olens.` In other Words, it comprises selectively promoting specific side reactions, other than polymerization of oleiins, in acid-catalyzed alkylation of parafiinswith oleiins.

One particularly noteworthy side reaction selectively promoted in accordance with the present invention results in the over-al1 effect of a hydrogen-transfer from the reactant paraiiln to the olenic reactant, followed by juncture of the resulting dehydrogenated paraiin or newly formed olefln" with unreacted paraffin. This reaction produces a by-product paraln having the same number of carbon atoms per molecule as the oleiinic reactant, and a product paraffin having exactly twice as many carbon atoms per molecule as the original paraffin in the feed. This reaction is particularly desirable when isobutane is being reacted with propylene, normal butenes, or amylenes, especially when a plentiful supply of isobutane is available, since the product contains large amounts of 2,2,4-trimethylpentane (isooctane) which is desirable because of its high octane rating.

Isobutane and propylene ordinarily yield 2,3- and 2,4-dimethylpentanes by simple parailinolen `iuncture, whereas they yield propane and octanes- (mostly isooctane) by the hydrogen transfer alkylation herein described. Isooctane has a higher octane rating (A. S. T. M. octane No.=100) than these dimethylpentanes (A. S. T. M. octane No.=82 and 89 respectively), and the theoretical yield of isooctane based on the weight of propylene in the feed is 271 per cent, which is considerably more than the theoretical yield of dmethylpentanes of 1 only 238 per cent. The by-product propane may be advantageously dehydrogenated in a dehydrogenation step to produce propylene and hydrogen, and the resulting propylene may be returned to the hydrogen transfer alkylation step.

Although the detailed mechanisms of all the reactions are not yet fully known, the following illustrative chemical equations (2 to 5, inclusive), deduced from data obtained by extensive experimentation, appear to account for some of the principal reactions of isobutane and propylene that can occur under the conditions herein disclosed, as contrasted with the conventional reaction (Equation l).

Simple paraffin-olefin juncture (Isobutane)- (Propyleno) (Dllnetliylpcntcnc) Hydrogen transfer-alkylaton CIB. HA 0381A (Propylcne) (Catalyst) (Propyl derivative) 3 ClHlA (Isobutyl derivative) (Propane) (Isobutane) (Catalyst) (lsobutylcnc) HA ClHsA (Isobutylcne) (Isobutane) (Isooctanc) asoascs isomerization-alkylation" and which normally occurs to only a relatively minor extent, is even more desirable since it avoids the formation of by-product normal butane. This reaction is selectively encouraged in some ways by conditions similar to those which encourage hydrogen transfer-alkylation; lt will be discussed hereinafter.

The simple iunctures of isobutane with amylenes yield nonanes, which have not yet been positively identified as to particular isomers. 'I'he reaction of this invention yields isooctane (2,2,4- trimethylpentane) as a product and pentanes as a by-product. 'I'his reaction occurs to an appreciable but minor extent under ordinary alkylating conditions, but by application of the principles of this invention it may be selectively greatly encouraged. The isooctane thus produced as a major product has a higher A. S. T. M. octane number than that of a nonane fraction normally produced (e. g., 91.6). Although the theoretical yield of octanes based on the weight of olefin in the feed by this hydrogen transferalkylation is slightly less than the theoretical yield of nonanes by ordinary alkylation, the byproduct pentanes are also useful for blending in gasoline and should be included in a consideration of the relative yields. Accordingly, the total theoretical yield of gasoline products (octanes plus pentanes) is 266 weight per cent for the hydrogen transfer-alkylation, or considerably more than that of 183 for the ordinary or simplejuncture alkylation.

Other examples of hydrogen transfer-alkylations are: isobutane and cycloolens to give octanes and by-product cycloparaftlns; isobutane and ethylene to give octanes and ethane; and the like. The reaction of isobutane and cycloolens, such as cyclohexene, proceeds readily under about the same conditions as the reaction of isobutane and normal butenes. is desirable to use a relatively high reaction temperature such as about 200 to 400 F., or a very active catalyst to obtain reasonably rapid reaction rates. One of the most satisfactory catalysts for use with ethylene consists of a mixture of substantially anhydrous hydrofluoric acid having a minor proportion, such as 1 to 10 per cent by weight, of boron fluoride; the small proportion oi boron fluoride has a strong promoting or enhancing effect on the catalytic action of the hydrouoric acid.

In the alkylation of isobutane with butylenes, in accordance with one modification of my invention, the over-all reaction already mentioned which may be termed olefin isomerization-alkylation tends to minimize differences in prod ucts obtained from different butylenes. That is, there is a tendency for any given butylene to isomerize, under alkylating conditions, to an equilibrium mixture of the various butylenes- If an equilibrium mixture (thermodynamic equilibrium) were actually obtained before any of the butylenes entered into the alkylation reaction, identical products would be obtained from each of the different butylenes. By the application of the present invention, the isomerization of normal butylenes prior to juncture with isobutane can be encouraged to the extent that butene-l gives a product which is similar to that hitherto normally obtained from butene2, and butene2 gives a product which approaches that hitherto ordinarily obtained only from isobutyiene.

Another desirable side reaction, which may be selectively encouraged in accordance with the principles of this invention, occurs normally only When ethylene is used, it,

to a minor extent in ythealkylation `oi' isopentane with olenns. This side reaction results in an apparent disproportionation of isopentane to isobutane and isohexanes (2- and 3-methylpentanes). For example, under some conditions, which are especially effective in the alkylatlon of isopentane with olens in the presence of anhydrous hydrofluoric acid, a surprisingly large proportion of the isopentane is converted to isobutane and isohexanes, concurrently with primary alkylation of another part of it, so that yields of hexanes and higher-boiling gasoline hydrocarbons as high as 500 or more per cent by ,weight of the olefin in the feed are obtained. This "disproportionation-alkylation" may be advantageously carried out in a combination alkylation-fractionation equipment wherefrom isobutane is distilled overhead, in company with some hydrofluoric acid, while the reactions are progressing. The isobutane produced by the disproportionation may be used as feed stock for other processes, as for a process in which it itself is alkylated; in the interest of an increased yield of higher-boiling or gasoline hydrocarbons from the disproportionation-alkylation, the isobutane is preferably removedl from the reaction mixture as soon as possible after formation, and it is preferably not recycled with unreacted isopentane to this particular process.

In addition to being based in part on the observation that in many alkylations using a liquid acid-type catalyst, especially hydrofluoric acid, certain side reactions lead to products which in specific instances are more desirable than the primary or simple parailin-olefin juncture products, the present invention in some of its features involves the following general principles:

1. Different reactions have dlierent temperature coeillcients of reaction rates, so that certain reactions may be selectively encouraged by selecting and controlling the temperature and the reaction time.

2. Over-all or mass reaction rates are dependent upon concentrations of reactants, so that certain reactions may be selectively encouraged by suitably controlling concentrations of reactants.

With respect to the first of these principles, in the concept of this invention, an increase in reaction temperature favors'hydrogen transfer-alkylation and disproportionation-alkylation, and disfavors olen isomerization-alkylation, relative to simple or primary alkylation. That is, increasing the temperature increases the reaction rates of hydrogen transfer and of disproportionation relatively more than the reaction rate of primary alkylation, and it increases the reaction rate of olefin isomerization relatively less than the reaction rate of primary alkylation. The practical temperature range is of course limited by excessive cracking reactions or decompositions at the upper limit and by disadvantageously low reaction rates at the lower limit. Within the practical temperature range, the optimum temperature for favoring the desired side reaction may be readily determined by trial for any particular case. For promoting hydrogen transfer-alkylation and disproportionation-alkylation, a temperature in the upper part of the practical range is to be preferred; for promoting olefin-isomerizationalkylation, a temperature in the lower part of the practical range is to be preferred. The practical temperature range varies somewhat with specific catalyst and reactants, but for the sake of con- -20 I". to about 300 P. for such a catalyst as hydrogen nuoride and for olelins other than ethylene. `The reaction temperature is interrelated with the reaction time, for the reaction time required to effect a given extent of reaction is generally shorter at a high temperature than at a low temperature.

With respect to the second of these principles, in general, the desired side reactions are preferentially favored if the concentration of free olefin is minimized by reaction with the catalyst before the olefin can react with the paraiiin by primary alkylation or with additional olefin by polymerization. Although oleiins readily add to hydrogen fluoride or undergo hydrofluorination, to form alkyl fiuorides, the part played by this reaction in primary paraiiin-oleiin and olefin-olefin Junctures in the presence of concentrated hydrofluoric acid as a catalyst is that of a reversible side reaction, not that of an intermediate reaction; that is, these primary juncture reactions comprise the additionof an activated parailin molecule or of an activated olefin molecule directly to a simple olefin molecule, and alkyl fluorides or similar oleln derivatives undergo these reactions only after being converted to simple oleflns. Hence, the rates of primary paraffin-olefin and olefin-olefin junctures are decreased by lowering of the concentration of free or uncombined olefin in the reaction zone. Conversely, the rates of the competitive side reactions, in which the olen appears to take part relatively more eilectively in the form oi' a compound or complex with the catalyst, asillustrated by Equations 2 to 5, are simultaneously increased. Specific examples of such side reactions are those involving hydrogen transfers, olefin isomerization, and the like.

Although one excellent method of obtaining maximum concentrations of combined olefin with minimum concentrations of free olefin evidently involves the direct use of alkyl compounds, such as alkyl fiuorides, alcohols. and the like, instead of olefins, as alkylating agents,'in practice this method makes necessary the use of a separate step for producing alkyl compounds from oleiins. A simple method not requiring such an extra step is advantageous in commercial applications. In accordance with one aspect of the present invention, results approaching the ideal are obtained by adding the oleiin to a parafflnic stream containing only a small proportion. of a suspended and/or dissolved liquid acid-type alkylation catalyst, to the total catalyst being roughly equivalent stoichiometrically to the total added olefin and giving the added olefin an opportunity to become combined. With'tlie limited quantity of catalyst, prior to introducing the stream into an alkylating zone, in which an excess of the same catalyst is present. Such a procedure differs from previous practice, in which it has been thought desirable to avoid contacting the olenywith the alkylating catalyst prior to introduction intothe alkylating zone, in order to minimize undesired olefin consumption by polymerization and hydropolymerization, which occur extenslvelywhen a-large separate catalyst phase is present. In accordance with the concept of this invention, however, in order to selectively promote desirable side reactions such as have been described hereinbefore, it is advantageous to contact the olefin with roughly an equivalent proportion of a hydrofluoric acid catalyst diluted by a large excess of paraffin hydrocarbons prior to introduction into the alkylatcreteness it may be said to be roughly from about 7s ing zone, since thereby the formation of catalystolefin addition products or complexes is favored without appreciable undesirable consumption of olefin by polymerization, hydropolymcrization, conlunct polymerization, and the like. nce formed, these addition products apparently do not react extensively with alkylatable paramns to produce the ordinary paramn-oleiinA juncture products until they are reconverted to olefins, either the same as the original olefins or different from them, thereby causing a delay in the effecting of paraffin-olefin junctures and consequently presenting opportunities for such desirable side reactions as hydrogen transfers, olefin isomerizations, and disproportionations to occur.

As the catalyst, liquid substantially anhydrous hydrofluoric acid is preferred because it ls advantageously appreciably soluble in parailln hydrocarbons and withal it is readily removable and/or recoverable from them. The solubility of hydrofluoric acid in parafllns is illustrated by the solubility of hydrofiuoric acid in isobutane, which has been experimentally determined to increase with temperature substantially linearly from 0.3 to 0.9 per centby weight in the temperature range of 32 to 140 F. A concentration of uniformly dispersed hydrofluoric acid of between about 0.6 and 4 per cent by weight is preferred. However, the invention is generally applicable with minor modifications to other liquid acid-type condensation catalysts, such as sulfuric acid, mixtures of sulfuric acid and hydrofiuoric acid, chlorosulfonic acid, fiuorosulionic acid, phosphoric acid, phosphoric acid-boron fluoride mixtures, aluminum chloride suspended or dissolved in various solvents, hydrofluoric acid containing small proportions of dissolved substances such as boron fluoride, and the like. H-i'drofluoric acid is usually preferred in many alkylations because it results in a more clean-cut reaction and the ranges of operating conditions used with it are generally broader and more readily controllable than with other catalysts. Since higher-than-usual temperatures are generally desirable in the practice of my invention, catalysts which act as oxidizing agents at such temperatures are often not suitable for use in the commerical practice of my invention. When ethylene and/or normal parafiins are reactants and hydrofluoric acid the catalyst, however, it is desirable to add a small proportion, such as l to l0 per cent by weight, of boron fluoride to the hydroiluoric acid to increase the activity of the catalyst.

An understanding of some aspects of this invention may be aided by reference to the drawing, which is a flow-diagram of one preferred arrangement of apparatus suitable for practicing the invention. This diagram obviously can not show all possible variations and minor modifications of the invention and should not be used to limit the invention unduly. For the sake of concrete illustrationbut without limiting the invention, the reactants will be assumed to be isobutane and propylene, and the alkylating catalyst will be liquid anhydrous hydrofluoric acid.

Propylene, which is a specific example of an olefin other than isobutylene having three to five carbon atoms per molecule, is admitted through inlet I0 into a stream of hydrocarbons flowing in conduit II and containing chiefly isobutane and a small proportion of dissolved and/or substantially uniformly dispersed or entrained substantially anhydrous hydrofluoric acid. The relative proportions of the two combining streams should preferably be such that the propylene is approximately molecularly equivalent to the hydronuoric acid. Although the optimum proportions have not been determined for all conditions. a mol ratio of hydrofiuoric acid to olefin of about 1.0:1 to 1.2:1 gives generally results close to the optimum, and mol ratios between about 0.75 and 3.0 generally give satisfactory results provided that no large local excess of hydrofluoric acid exists as a separate liquid phase. 'The exact optimum mol ratio for any given instance depends upon several factors, such as degree of dilution by paraillns, temperature, time, agitation or mixing efficiency, and individual characteristics of the particular olefin used, but it can be readily determined for any particular case by trial.

The combined stream from conduit II flows into time tank I 2, wherein the stream resides only sufficiently long for the major part of the olefin to react with hydrogen fluoride to form the corresponding alkyl uoride, such as isopropyl fluoride, which is formed when the olefin is propylene. Means of agitation suillcient to insure thorough mixing of the reactants may be provided. but usually adequate mixing may be obtained in conduit II by using turbulent flow conditions or a sufficiently long conduit, although time tank I2, when it is more than a simple extension of conduit I I, may be baiiled, or packed, as with an inert granular material, or provided with transverse perforated plates to aid commingling of the reactants. The residence time in time tank I2 may vary Within a wide range, for example from about 1 minute to an hour or more, depending upon temperature, concentrations of olefin and hydrogen fluoride, and specific properties of the particular olefin used. These variables are easily correlatable by a few trial runs for any particular system by one skilled in the art. When the olefin is propylene, a temperature of about F., olefin and hydrogen fluoride concentrations in the range ofabout 2 to 10 mol per cent of the total combined stream, anhydrous hydrogen fluoride and a time in the range of 5 to 15 minutes give good results; when the olefin is one or more of the butylenes and amylenes, the time may -be appreciably shorter- It is not necessary that the hydrofiuorination of the olefin proceed to completion, or to the thermodynamic equilibrium, but only that a substantial part of the olefin become combined with the hydrofiuoric acid, so that the concentration of free olen, which in the presence of liquid hydrofluoric acid results in paraffin-olefin and olefin-olefin junctures, ls minimized.

From time tank I2, the mixture flows through conduit I3 to reactor Il. Reactor I4 may be any suitable vessel resistant to corrosion by hydrofluoric acid and provided with a mixing device, such as one or more jet-type and/or perforated plate-type inlets, baiiles, or stirrers, capable of maintaining the hydrocarbon and the hydrofluoric acid in a state of intimate mixture. Liquid concentrated or substantially anhydrous hydrofluoric acid is introduced to reactor I4 through conduit I5. The relative proportions of hydrofiuoric acid and hydrocarbon and the conditions of temperature and pressure in reactor I4 should be such that two distinct liquid phases are present. Usually a volume ratio of hydrofiuoric acid to hydrocarbon in the range of 0.3:1 to 2: 1 is preferred and the optimum ratio appears to be 1:1, however, volume ratios outside this range may be used, although if they are much higher or lower, good contacting of acid with hydrocarbon becomes relatively dlmcult to maintain. The temperature may be in the range of about to 200 F.. a temperature above about 100' F. is preferred and is readily obtained because the overall heat effect from the reactions is exothermic. 'I'he pressure need be sufllcient only to maintain the reaction mixture in a liquid or dense-phase condition.

After a suitable average residence'time in reactor i4, for example a time in the range of 1 to 30 minutes, the reaction mixture passes through conduit I6 to settler l1, where it is separated as by vgravitational and/or centrifugal means, into two liquid phases. Most of the denser or hydrofluoric acid phase is recycled through conduits il and I to reactor I4; a small proportion is usually passed through conduit I! to acid-rerun column 20 for purification before re-use. A part of the lighter or hydrocarbon phase may be recycled through conduit 2l to conduit Il, wherein it dilutes the incoming olefin and carries dis'- solved or entrained hydrouoric acid to react wih the olefin. The remainder. or all, of this phase is passed through conduit 22 to deisobutanizer 23, wherein it is separated into two fractions, a lowboiling fraction comprising isobutane and propane and minor amounts of hydrofluoric acid, and a high-boiling fraction comprising higherboiling product parafilns, mostly gasoline-range parafllns. The low-boiling fraction is passed through conduit 24 to depropanizer 25, and the high-boiling fraction is passed through conduit 26 to deiluorinator 21, or directly to fractionating means 43 through conduit 5i.

Depropanizer 25, which also includes means for removing hydrofluorio acid, separates propane from isobutane. The propane is passed through conduit 28 to dehydrogenator 29, wherein it is cracked noncatalytically or, preferably, dehydrogenated catalytically to produce propylene. Additional propane may be introduced to dehydrogenator 29 through inlet 30.Y

Propylene-containing efiiuent from dehydrogenator 29 is passed through conduit 3i to co1- umn 32, wherein hydrogen, methane, and other materials boiling lower than propylene are separated and are removed therefrom through conduit 33. The propylene may be concentrated by being fractionally distilled and then may be used as olenio feed to the hydrofluorination and alkylation steps, but it is preferably rpassed to gether with the propane directly through conduit 34 to conduit Il as the olefinic feed., The propane acts as a desirable inert material in the reaction zone. Although, in ordinary alkylations. inerts are usually considered undesirable because of adverse effects upon equipment capacities, the presence of inert materials is somewhat advantageous in the present process by selectively `promoting desirable reactions such as hydrogen-transfer reactions. Apparently the advantage results from a decrease in the rate of primary parailln-olen junctures, owing to a lowering of the isoparafn concentration in the reaction zone, thus increasing the proportion of olefin undergoing hydrogen transfer priorto addition to the isoparailin. Similarly, the presence of inerts promotes isomerzations of l-olefins to 2-olefins and of secondary oleflns apparently to isoolens prior to alkylation in systems in which normal butylenes and/or amylenes are used to react with isobutane.

Isobutane from the bottom of depropanizer 25 is passed through conduit 35 to saturator '38 whereinv it is agitated and Abecomes saturated with hydroiiuoric acidadmitted through conduit 21.,

Additional isobutane is introduced through inlet l0, to replace that consumed in the process.

The isobutane-hydroiluoric acid mixturefrom saturator 34 passes through conduit-38 to settler 33 wherein it is separated, as by gravitational and/or centrifugal means, into two liquid phases. The separation is preferably incomplete -to the extent that the upper phase contains not only dissolved hydrouoric acid but also a minor proportion of substantially uniformly dispersed or entrained hydrofluoric acid, so that the total hydrofluoric acid associated with said upper phase. as it is removed from settler 39 through conduit 40, amounts to about 2 to 6 per cent by weight of the upper phase. This upper phase, comprising isobutane-and a minor proportion of hydrofluoric acid, is passed through conduit 40 to'conduit Il, wherein it serves to dilute the propylene and to supply most of the hydrofiuoric acid for reaction with it.v The lower, or hydroiluoric acid phase, is recycled through conduit 4I to reactor i4.

In defluorinator 21 the deisobutanized material from deisobutanizer 23, is passed over a contact material having some degree of catalytic dehydrogenation power, such as a supported nickel catalyst, or, more economically, a granular aluminous material such as bauxite or fuller's earth, at a temperature in the range of about 200 to 500 F., to remove organically combined fluorine. The fluorine-free product material passes through conduit 42 to fractionating means 43.

Fractlonating means 43 may consist of one or more columns suitably designed for separating `the total product material into desired fractions,

such as a major gasoline-range fraction, which may be withdrawn through outlet 44, and a minor high-boiling fraction, which may be withdrawn through outlet H5. Substantially pure isooctane may be advantageously separated as a major fraction and maybe withdrawn through outlet 46, instead of being left in the gasoline-range fraction.

Acid column 20 separates used hydrofluoric acid into a major overhead fraction of substantially pure or anhydrous hydrofluoric acid and a bottom fraction of tar, water, and other impurities which gradually accumulate in the acid during use. The overhead fraction is recycled through conduit 41 to reactor i4 and/or to saturator 36. outlet t8. Make-up acid enters the system at some point such as inlet 49.

lt will be understood that the flow-diagram is schematic and that auxiliary equipment, not shown or described, such as pumps, valves, controllers, and the like, may be desirable or even necessary at various points in the process. As

" such auxiliary equipment are well-known, they can be readily supplied by those skilled in the art.

As has already been indicated, other oleins, such as the butylenes and the amylenes, may be used instead of propylene. However, in practical applications of this invention to the conversion of low-boiling isoparains, some choice as to Darticular olens is sometimes desirable. For example in the alkylation of isobutane with isobutylene, the preliminary hydrouorlnation step of this invention is of no such noteworthy advantage as it is in the alkylation of isopentane with isobutylene. The reason for this differentiation is that the delay in paraffin-olefin junc- The impurities are withdrawn through ture eil'ected by the preliminary hydrofiuorination of isobutylene leads to no discernible advantage when the original isoparamn is isobutane, since the nature of the product is not improved, whereas this hydrouorination leads to increased disproportionation to isobutane and isohexanes when the isoparafiln is isopentane. The invention is of most practical benefit in the alkylation o1' isobutane with secondary or normal olens having three to five carbon atoms per molecule, as both the hydrogen-transfer and the olefin-isomerization reactions favored by it lead to the production oi' product paraillns of advantageously relatively high octane rating. In the alkylation of isopentane, an advantage of the invention is most marked when the olefin is butene-l, for upon isomerization oi' this olefin and upon subsequent Juncture of isopentane with the resulting butylene isomer, product paraiilns oi higher oc tane rating are obtained than when the olefin in the paraflin-olen juncture is the original butene-l. Insofar as disproportionatlon of isopentane to isobutane and isohexanes is concerned, it may be noted that the presence of the added olefin in some form or other is advantageous, since it has been found experimentally that the disproportionation proceeds relatively very slowly, if at all, when no olefin or olefin derivative is present.

The following examples are illustrative of some of the many aspects of the invention without being necessarily limitative.

Exmu: I

Two test runs were made, in a. steel batch-type stirrer-equipped reactor, for reacting isobutane and propylene in the presence of anhydrous hydroiluoric acid at about 110 F. The first run was made under what may be termed ordinary alkylating conditions; that is, the propylene was added as a vapor directly to a well-agitated twoliquid-phase mixture ot approximately one volume of hydrouoric acid and three volumes of isobutane, or an approximately ninefold molecular excess of isobutane. The second run was made similarly but under what may be termed selected conditions; that is, the propylene was added as a vapor at one-sixth of the rate used in the first run, the addition being made at a high and relatively quiescent point in the reactor at which the wall was only wetted by the mixture of isobutane and hydrofluoric acid, so that a considerable part of the propylene formed isopropyl fluoride before becoming mixed with the main body of the well-agitated two-liquid-phase mixture of isobutane and hydrofiuoric acid. The conditions in this second run were thus relatively favorable to the occurrence of hydrogen transfer from isobutane to propylene prior to rapid alkylation. since the propylene came into contact for a relatively long time with only a limited amount of hydroiluoric acid, which was sufiicient to form isopropyl fluoride but was relatively insuillcient to act as a catalyst promoting ordinary alkylation and/or polymerization. The reactions were stopped by Stpping the stirring and by letting the reaction mixture separate into two liquid layers when the propylene had been in the reactor for 11.5 to 16.0 minutes in the first run and 7.0 to 25.0 minutes in the second run; thus the calculated average reaction time was about the same in both runs, being 13.8 minutes in the rst and 16.0 minutes in the second. The yields of liquid parafns were about the same in both runs. but the quantitative proportions of the individual asoases paraiiins differed greatly, lowing data:

Composition of product, volume per cent as is shown by the tol- The product from the run made under selected conditions had more than twice as much isooctane (2,2,4-trimethylpentane) as that from the run made under ordinary conditions, and in consequence it had a considerably higher antiknock rating. The fact that it had a relatively somewhat higher content of high-molecularweight compounds should not be construed as a disadvantage, for the run was made under conditions that were exploratory and far from optimum, so that an undesirable amount of polymerization actually occurred because of the presence of some excess liquid hydrofiuorc acid during the hydrofluorination of the propylene; under more closely controlled conditions, as when the propylene is added to isobutane containing substantially only a minor proportion of entrained and/or dissolved hydroiluoric acid, such polymerizatlon is virtually eliminated. l

EXAMPLE II In a batch-type run made at 97 to 105 F. in an l8-liter steel reactor provided with a 540-R. P. M. stirrer, liquid isobutane was thoroughly mixed with about a third of its volume of liquid anhydrous hydrofiuoric acid, and 0.10 of its molecular equivalent of isopropyl iluoride, which had been made by reacting propylene and anhydrous hydrouorc acid, was added at a uniform rate during 13 minutes. The reaction mixture was stirred for an additional 7 minutes, so that the reaction time was 7 to 20 minutes. or an average of 13.5 minutes. The reaction mixture was then separated into two liquid phases, and the upper or hydrocarbon phase was freed from acid and was fractionally distilled to recover the liquid product. This product amounted to 226.4 per cent by weight of the propylene equivalent of the isopropyl fluoride. Its composition in per cent by volume was: hexanes, 3.7; heptanes, 36.6; octanes (mostly isooctane), 55.2; heavier paraiiins, 4.5. The aviation-gasoline fraction, cut at 376 F., amounted to 99.7 per cent by volume and had an octane number of 93.4.

EXAMPLE III In a continuous process similar to that shown in the drawing, propylene is added to a liquid stream of isobutane containing about 2 to 4 per cent by weight of dissolved and entrained (nely subdivided) hydrouoric acid, in a proportion approximately molecularly equivalent to the hydrofluoric acid. The stream, which is at about F. and is sufllciently well agitated to prevent settling into two rliquid layers, passes through a time tank, in which a major part of the propylene forms isopropyl fluoride during a residence time of about l0 to l5 minutes, and then into a reactor in which it is thoroughly mixed with about a third to a half of its own volume of substantially anhydrous liquid hydrofiuoric acid.

After a residence of about to 15 minutes in this reactor, the mixture of hydrocarbons and hydrotluorlc acid passes to a settler for separation into two liquid layers. The lower or hydrouoric acid layer is partly recycled to the reactor and partly passed to a fractionation system for purification by distillation before re-use. The upper orhydrocarbon ylayer is fractionated and treated substantially as already described, in such a Way that propane is Awithdrawn from the process; that unreacted isobutane is recycled together with concomitantly distilled hydroiiuoric acid and with acid from the acid-purification system, to the propylene-addition step; that a small proportion, usually only a fraction of 1 per cent, of hydrocarbons boiling above the gasoline range is removed; and that a liquid gasoline range product is obtained in high yield. Of this gasoline-range product, about 50 to 60 per cent by volume boils in the octane range; over 30 per cent by volume, usually 35 to 40 per cent by volume is isooctane (2,2,4-trimethylpentane) and can be readily separated during the fractionation as a separate product of the process. Because of its high content of isooctane, the total gasoline-range product has an A. S. T. M. octane rating of about 92 to 94.

EXAMPLE IV When butene-l is used instead of propylene in the process of Example III, the gasoline-range product has an A. S. T. M. octane rating about two to three units higher than that of the gasoline-range product obtained by the ordinary alkylation process from the same quantities of materials under substantially the same conditions except that the preliminary hydrofluorination of the olefin is omitted. Thus, instead of an octane number of about 89 characteristic of the product obtained by ordinary alkylation of rating illustrates the advantage obtained by the present invention. presumably through hydrogen transfer and/or olefin isomerization.

EXAMPLES V T0 X Data for several batch-type runs for the conversione! isopentane in the presence oi hydroiluorlc acid, using various olens, are presented together, for the sake of brevity and conciseness, in the following tabulation.

In the' run with propylene, Example V, the amount of isobutane formed was not determined, but it. was probably approximately molecularly equivalent to the hexanes (isohexaneskvwhich constituted over 30' per cent ofthe'l'quid product. 'Ihis run was made at an insufficiently high temperature for optimum results, but it is clear than a high extent of disproportionation occurred in spite of this fact.

Among other things. it may be noted from these data that the yield of depentanized liquid product was much higher than that to be expected from ordinary alkylation, being as high as over twice the theoretical alkylation yield computed on the basis of one molecule of olefin reacting with one molecule of isopentane. Yields even higher than those shown are obtained at relatively higher temperatures, such as temperatures in the preferred range of 100 to 200 F. With respect to the two runs made with isobutylene, the yield was highest in the run that was made at the relatively higher temperature. Temperatures below about 40 F. are relatively disadvantageous. In all these runs, more than one molecule of isopentane reacted permolecule of olefin to give higher-boiling paraflins; indeed, in the higher-temperature run With isobutylene over ve molecules or isopentane reacted per molecule of olefin. Since olens, because of their relatively greater readiness to react chemically, are in general more valuable than the corresponding parafns, a. major advantage of` the disproportionation-alkylation here exemplified is obvious.

Disproportlona/tion-alkylaton of isopentane Example V VI VII VIII IX X Olen CsHs i-C4Ha i-C4Hs l-CHs 2C Hg C5111@ Temperature, F. 66-79 64-86 38-61 66-100 68-102 'i3-100 ReaCtiOn time, min 35. 10-30 10-30 10-30 l0-30 9-31 isopentane/olefin (mol. (feed). 7. 25 8. 75 7. 62 8. 31 7. 5 10. 2 Hydrocarbons/HF (vol.) 7. 6 1 l 1 1 y Isobutane formed, Wt. per cent of oletln. 261 200 155 187 165 Pentane-free liquid product:

Yield- Wt. per cent of olen 406 535 443 405 445 437 Wt. per cent of theoretical alkylation yield 136 234 194 177 195 2lb Composition, vol. per cent- Hexanes. 30. 7 45. 2 42. 3 37. 7 41. 4 49. 5 Heptanes. 8. 8 l0. 2 9. 0 5. l 6. 7. 5 Octanes... 41. 7 5. 8 11. 6 6. 4 7. 7 3. 4 Nonanes. (2i 37. 0 32. 2 9 Decanes .4 Havier.-- 3. 4 2.o 4. 3 1&8 11 2. a

Total 100. 0 100.0 100. 0 100. 0 100. 0 100. 0 Aviation-gasoline fraction- Cut point, F 338 289 289 284 293 295 Yield, vol. per cent.. 95. l 8l. 4 76. 2 80. 7 84.3 78. 0 Reid vapor pressure. 3. 2 4. 65 4. 60 4. 45 4. l0 5. l5 Gravity, API 71. 2 75. 6 75. 2 74. 6 73. 7 76. 4 ASTM distillation, F.-

First drop 138 143 143 142 145 140 l0 per cent evap 173 153 155 155 )H1 150 50 per cent evap 213 175 177 183 191 1mi per cent evep. 274 264 273 271 286 2M nd point 344 334 328 321 336 33'? ASTM octane No.-

0 cc. TEL 75. 0 75. 0 76. 2 74. 6 79. 2 72. 2 l cc. TEL 88. 7 90.1 87. 7 89. 3 86. 2i Total products, wt. per cent ot ol 796 643 560 632 i.'

Another major advantage is provided by the exceedingly high yield of concomitantly formed isobutane, whichl was of the order of twice the original olefin by weight. 'Ihis isobutane is of particular value because present sources of this hydrocarbon are inadequate to meet the demand for isobutane as a feed for the manufacture of high-octane aviation gasoline by alkylation. Therefore, this concomitantly formed isobutane may be advantageously separated, preferably as soon as possible after formation, and it may be alkylated with an olen to aviation-gasoline par1 aillns in a separate alkylation unit, preferably in the presence of hydrofluoric acid as catalyst. This procedure is relatively more advantageous than recycling th'e isobutane together with unreacted isopentane back to the first or isopentanealkylation unit, for the over-al1 yield of gasolinerange liquid paraillns for the two-stage operation is considerably larger than for the one-stage operation. Furthermore, the liquid product from the alkylation of isobutane is considerably higher in octane rating than the liquid product from the disproportionation alkylation of isopentane with the same oleiln; for example, the aviation-gasoline alkylate from hydrofluoric acid alkylation of isobutane with isobutylene has an octane number of about 95-96, which is 20 units higher than the values given in the foregoing tabulation for the aviation-range fraction of the product from the conversion of isopentane. Hence, because of the present demand for high-octane aviation gasoline, the two-stage operation yielding two gasoline range products is relatively more advantageous than the one-stage operation having combined recycling of isobutane and unreacted isopentane. However, this one-stage operation is not outside the broadest scope of this invention.

The isohexanes produced by the disproportionation may be similarly advantageously separated from the product, as by fractional distillation, and may be used as such for blending in motor fuels or may be alkylated with an olein, as in the presence of hydrouoric acid, to give paraiiins of different volatility.

It should be observed that the reactions promoted in accordance with this invention do not comprise secondary reactions such as for example that of cracking subsequent to ordinary alkylation. In such cracking-alkylation, the reactant isoparaffin is alkylated with an olefin as in ordinary alkylation and the resulting alkylate is allowed to crack into smaller compounds. Obviously, such cracking-alkylation results in little or no improvement in the over-al1 yield of parafilns heavier than the original paramn, whereas by the present invention the over-all yield of such heavier paraiiins is markedly increased, and to a surprisingly and quite unexpectedly high degree in the light of past knowledge. Briefly, instead of promoting reactions following alkylation, the present process promotes reactions preceding or accompanying alkylation.

In accordance with this invention, certain desirable reactions are selectively promoted that ordinarily occur to only relatively minor extents in alkylations of paraflins with olefins in the presence of liquid acid-type alkylation catalysts. Because the invention may be practiced otherwise than as speciiically described or illustrated, and because many modifications and variations within the spirit and scope of it will be obvious to those skilled in the art of hydrocarbon conversion, the invention should not be unduly restricted by the 2iforegoing specification and examples.

I claim:

1,. A process for converting propylene and isobutane into propane and octanes, which comprises admixing propylene at a temperature between about and about 200 F. with a liquid mixture comprising isobutane and hydrogen fluoride, said hydrogen uoride comprising between about 2 to 6 per cent by weight of said liquid mixture, in an amount such that the mol ratio of hydrogen fluoride to olefin is between about 1.0:1 and 1.2:1, maintaining said admixture for a period between about 5 to 15 minutes, subsequent to said period adding and intimately admixing additional hydrogen iluoride in an amount such that the volume ratio of total liquid hydrogen fluoride to total hydrocarbon is between about 0.3: 1 and 2: 1 in the resultant mixture, and maintaining the last said liquid admixture at a reaction temperature between about 100 and about 200 F. for a. reaction time not greater than about 30 minutes to form propane and octanes.

2. A process for converting propylene and isobutane into propane and octanes, which comprises intimately admixing liquid isobutane and liquid concentrated hydrofiuoric acid to form a saturated solution of hydrogen fluoride in said liquid isobutane, separating the major portion of the undissolved hydrofluoric acid from said admixture and leaving a liquid comprising isobutane saturated with hydrogen iluoride and sufiicient excess hydrofluoric acid that the total hydrogen fluoride amounts to about 2 to 6 per cent by weight of the total, admixing propylene with said liquid in an amount such that the mol ratio of hydrogen fluoride to olen is between Vabout 1.0:1 and 1.2:1 and maintaining said admixture at a temperature between about 100 and 200 F. for a period between about 5 to 15 minutes, subsequent to said period adding and intimately admixing additional liquid concentrated hydroiluoric acid in an amount such that the volume ratio of total liquid hydroiiuoric acid to hydrocarbon is between about 0.3:1 and 2:1 in the resultant mixture, and maintaining the last said liquid admixture at a. reaction temperature between about 100 and about 200 F. for a reaction time not greater than about 30 minutes to form propane and octanes.

3. A process for converting a low-boiling normal olefin and a low-boiling isoparaflin into at least two different parafllns, one corresponding to said normal olefin and one having twice the number of carbon atoms per molecule as said isoparailln, which comprises intimately admixing a low-boiling normal olen with a liquid comprising a paralnic hydrocarbon material, comprising a lowboiling isoparain, saturated with hydrogen iiuoride and associated with suillcient excess hydrogen fluoride that the total hydrogen fluoride amounts toabout 2 to about 6 weight per cent of the total liquid, the mol ratio of hydrogen iluoride to added normal olen being between about 1.0:1 and 1.2:1, maintaining said admixture at a temperature between about 100 and about 200 F. for a period between about 5 and about 15 minutes, subsequent to said period adding and intimately admixing with the resultant 4material concentrated liquid hydrofluoric acid in an amount such that the volume ratio of total liquid hydrouoric acid to total hydrocarbons is between about 0.3: 1 and about 2:1 in the resultant mixture, and maintaining the last said liquid admixture at a reaction temperature between about 100 and 200 F. for a reaction time not greater than about 30 minutes to form a parailln hydrocarbon corresponding to said low-boiling normal olefin and a. paramn hydrocarbon having twice the number of carbon atoms per molecule as said low-boiling soparan.

4. The process of claim 3 in which propylene and isobutane are converted to propane and octanes.

5. The process of claim- 3 in which a. normal butylene and isobutane are converted to a butanoA and octanes.

6. The process of claim 3 in which butene-l and isobutane are converted to a. butane and octanes.

7. The process of claim 3 n which a norma; butylene and isopentane are converted to a butane and decanos.

MARYAN P. MATUSZAK. 

